In organisms with complex life cycles living in seasonal environments, the synchronisation of phenological events is important from the ecological and evolutionary perspectives. Life history ...transitions should be synchronised to a greater degree at northern latitudes. We quantified hatching and emergence timing and synchrony in the obligate univoltine damselfly Lestes sponsa along a latitudinal gradient covering its entire north–south range in Europe. In our first experiment, populations from different latitudes were grown in separate climate chambers simulating temperature and photoperiod conditions occurring at their sites of origin. Northern populations expressed early and high synchronous hatching and emergence, central populations intermediate, and southern populations late and low synchronous hatching and emergence. This pattern was expressed at both population and full‐sibling family levels, indicating stronger selection for timing and synchronisation in the north compared to the south. In our second experiment, populations from all latitudes were reared in conditions simulating an average temperature and photoperiod over the latitudinal gradient. Interestingly, the pattern of timing and synchronisation was reversed with respect to latitude when compared to the pattern shown in the first experiment, indicating the importance of environmental factors in shaping phenological events. Our results indicate strong selection for timing and synchronisation of life history events at northern latitudes, caused by time constraints. Our results also show that it is important to use as natural conditions as possible in experiments on life history shifts in organisms with complex life cycles in order to achieve a correct understanding of these shifts.
According to classic ecological models, nonterritorial males should settle in low-quality habitats as a result of losing competition over reproductive sites (‘defeated male’ hypothesis). ...Alternatively, according to evolutionary game theory models, nonterritorial males should settle in the vicinity of high-quality sites and ‘choose’ to delay breeding until these habitats are vacant for them (‘male player’ hypothesis). However, nonterritorial male spatial distribution has not been experimentally tested. If the defeated male hypothesis is true (1) deterioration of high-quality sites should increase the number of nonterritorial males in a population and (2) vacated low-quality territories should be taken over by new territorial males. If the male player hypothesis is true, a similar manipulation should (1) decrease the number of nonterritorial males and (2) vacated low-quality territories should not be taken over. We performed two types of field experiment to test these hypotheses: male removal and patch quality manipulation. Our study species was the territorial damselfly Calopteryx splendens; males of this species exhibit both territorial and nonterritorial behaviour. Our results suggest that deterioration of high-quality habitats significantly reduced the number of nonterritorial males. The proportion of take-overs of the high-quality territories was significantly higher than that of low-quality territories. Our study supports the assumptions of the male player hypothesis and indicates that nonterritorial damselflies are more sensitive to habitat quality changes than territorial ones. Because nonterritorial individuals exist in most populations of territorial taxa, a better understanding of their settlement rules may be relevant for population dynamics and modelling.
•We investigated the effect of habitat quality on the settlement of floaters.•Habitat disturbances affect mostly the nonterritorial part of a population.•Vacated high-quality territories are always taken over by new residents.•Nearly half of vacated low-quality territories are not taken over.•Floaters settle in the vicinity of high-quality sites.
Accumulating data indicates that following anti-cancer treatments, cancer cell death can be perceived as immunogenic or tolerogenic by the immune system. The former is made possible due to the ...ability of certain anti-cancer modalities to induce immunogenic cell death (ICD) that is associated with the emission of damage-associated molecular patterns (DAMPs), which assist in unlocking a sequence of events leading to the development of anti-tumour immunity. In response to ICD inducers, activation of endoplasmic reticulum (ER) stress has been identified to be indispensable to confer the immunogenic character of cancer cell death, due to its ability to coordinate the danger signalling pathways responsible for the trafficking of vital DAMPs and subsequent anti-cancer immune responses. However, in recent times, certain processes apart from ER stress have emerged (e.g., autophagy and possibly viral response-like signature), which have the ability to influence danger signalling. In this review, we discuss the molecular nature, emerging plasticity in the danger signalling mechanisms and immunological impact of known DAMPs in the context of immunogenic cancer cell death. We also discuss key effector mechanisms modulating the interface between dying cancer cells and the immune cells, which we believe are crucial for the therapeutic relevance of ICD in the context of human cancers, and also discuss the influence of experimental conditions and animal models on these.
A wealth of evidence shows that combinations of ecological stressors interact in shaping life history traits, but little is known about how ecological stressors combine with different seasonal time ...constraints to shape life history, behavior and mortality across populations. We studied life history, behavior and mortality rate in two latitudinally distant populations of the strictly univoltine, adult‐overwintering damselfly Sympecma fusca. Results from laboratory common‐garden and outdoor experiments indicated countergradient variation of larval development time and growth rate: the more time‐constrained larvae showed faster development and a higher growth rate. This finding led to larger size at emergence in the more time‐constrained individuals. Under conditions of intraspecific interaction (outdoor experiment), northern individuals showed lower survival than southern ones, presumably due to cannibalism. In the absence of intraspecific interactions (laboratory experiment), northern and southern larvae did not differ in survival. Finally, laboratory‐grown northern and southern larvae did not differ in activity level. This is the first time that compensation for seasonal time constraints has been shown in a temperate odonate species that overwinters in the adult stage.
In order to predict evolutionary responses to environmental changes one needs to identify the evolutionary potential in terms of genetic variation of traits and of the traits' plasticity. We studied ...genetic variance in life history traits and their reaction norms in response to manipulated photoperiods in central, northern, and northernmost peripheral populations of the damselfly Lestes sponsa (Hansemann). After the central‐marginal hypothesis, it is predicted that central populations will express the highest genetic variance. Northern and northernmost populations showed the highest development and growth rates. All populations expressed shorter development and accelerated growth when raised in a northern compared with a central latitude photoperiod. The slopes of reaction norms differed between regions resulting in a region‐by‐photoperiod interaction. There was genetic variation in development time; however, it did not differ across regions. There was no genetic variation in growth rate or in the plasticity of development time and growth rate to photoperiod. Results did not support the central‐marginal hypothesis. However, evidence was found that the development time has the potential to evolve at similar rates across study regions. In contrast, the growth rate seems to be genetically constrained for further evolution, probably because of a strong past directional selection on this trait. The presence of low genetic variation in the slope of the reaction norms could be a result of stabilising selection imposed by seasonality.
Winter diapause consists of cessation of development that allows individuals to survive unfavourable conditions. Winter diapause may bear various costs and questions have been raised about the ...evolutionary mechanisms maintaining facultative diapause. Here, we explored to what extent a facultative winter diapause affects life-history traits and the transcriptome in the damselfly Ischnura elegans, and whether these effects were latitude-specific. We collected adult females at central and high latitudes and raised their larvae in growth chambers. Larvae were split into a non-diapausing and post-winter (diapausing) cohort, were phenotyped and collected for a gene expression analysis. At the phenotypic level, we found no difference in survival between the two cohorts, and the post-winter cohort was larger and heavier than the non-winter cohort. These effects were mostly independent of the latitude of origin. At the transcriptomic level, wintering affected gene expression with a small fraction of genes significantly overlapping across latitudes, especially those related to morphogenesis. In conclusion, we found clear effects of diapause on the phenotype but little evidence for latitudinal-specific effects of diapause. Our results showed a shared transcriptomic basis underpinning diapause demonstrated, here, at the intraspecific level and supported the idea of evolutionary convergence of the response to diapause across organisms.
Photodynamic therapy is a promising antitumor treatment modality approved for the management of both early and advanced tumors. The mechanisms of its antitumor action include generation of singlet ...oxygen and reactive oxygen species that directly damage tumor cells and tumor vasculature. A number of mechanisms seem to be involved in the protective responses to PDT that include activation of transcription factors, heat shock proteins, antioxidant enzymes and antiapoptotic pathways. Elucidation of these mechanisms might result in the design of more effective combination strategies to improve the antitumor efficacy of PDT. Using DNA microarray analysis to identify stress-related genes induced by Photofrin-mediated PDT in colon adenocarcinoma C-26 cells, we observed a marked induction of heme oxygenase-1 (HO-1). Induction of HO-1 with hemin or stable transfection of C-26 with a plasmid vector encoding HO-1 increased resistance of tumor cells to PDT-mediated cytotoxicity. On the other hand, zinc (II) protoporphyrin IX, an HO-1 inhibitor, markedly augmented PDT-mediated cytotoxicity towards C-26 and human ovarian carcinoma MDAH2774 cells. Neither bilirubin, biliverdin nor carbon monoxide, direct products of HO-1 catalysed heme degradation, was responsible for cytoprotection. Importantly, desferrioxamine, a potent iron chelator significantly potentiated cytotoxic effects of PDT. Altogether our results indicate that HO-1 is involved in an important protective mechanism against PDT-mediated phototoxicity and administration of HO-1 inhibitors might be an effective way to potentiate antitumor effectiveness of PDT.
Large-scale latitudinal studies that include both north and south edge populations and address sex differences are needed to understand how selection has shaped trait variation. We quantified the ...variation of flight-related morphological traits (body size, wing size, ratio between wing size and body size, and wing shape) along the whole latitudinal distribution of the damselfly Lestes sponsa, spanning over 2700 km. We tested predictions of geographic variation in the flight-related traits as a signature of: (1) stronger natural selection to improve dispersal in males and females at edge populations; (2) stronger sexual selection to improve reproduction (fecundity in females and sexual behaviors in males) at edge populations. We found that body size and wing size showed a U-shaped latitudinal pattern, while wing ratio showed the inverse shape. However, wing shape varied very little along the latitudinal gradient. We also detected sex-differences in the latitudinal patterns of variation. We discuss how latitudinal differences in natural and sexual selection regimes can lead to the observed quadratic patterns of variation in body and wing morphology via direct or indirect selection. We also discuss the lack of latitudinal variation in wing shape, possibly due to aerodynamic constraints.
Predation is ubiquitous in nature. One form of predation is cannibalism, which is affected by many factors such as size structure and resource density. However, cannibalism may also be influenced by ...abiotic factors such as seasonal time constraints. Since time constraints are greater at high latitudes, cannibalism could be stronger at such latitudes, but we know next to nothing about latitudinal variation in cannibalism. In this study, we examined cannibalism and activity in larvae of the damselfly Lestes sponsa along a latitudinal gradient across Europe. We did this by raising larvae from the egg stage at different temperatures and photoperiods corresponding to different latitudes.
We found that the more seasonally time-constrained populations in northern latitudes and individuals subjected to greater seasonal time constraints exhibited a higher level of cannibalism. We also found that activity was higher at north latitude conditions, and thus correlated with cannibalism, suggesting that this behaviour mediates higher levels of cannibalism in time-constrained animals.
Our results go counter to the classical latitude-predation pattern which predicts higher predation at lower latitudes, since we found that predation was stronger at higher latitudes. The differences in cannibalism might have implications for population dynamics along the latitudinal gradients, but further experiments are needed to explore this.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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